The invention relates to a hydrocephalus valve with an electrical actuating system, comprising a control system opening and closing the hydrocephalus valve.
In the case of people suffering from hydrocephalus there is the problem that raised internal pressure of the brain occurring because of excessive cerebrospinal fluid leads to serious problems for the people affected. The brain tissue is therefore damaged and permanently weakened and there are various symptoms such as dizziness, walking difficulty, headaches, nausea, sickness and dementia. Untreated, the disease can ultimately lead to the death of the patient. The type and extent of the symptoms occurring depend on the causes underlying the disease, general constitution, but primarily the age of the patient. In babies, the rise in pressure brings about an unnatural growth of the head; in adults, the substance of the brain is lost in favour of the water content in the interior of the skull.
There has only been a successful possibility for treating people suffering from hydrocephalus for about 50 years. For this an artificial drainage device is implanted which allows the drainage of the cerebrospinal fluid into other body regions in which the fluid which has been discharged, can then be broken down. Control of the drainage is undertaken here by valves which are intended to ensure the required pressure in the interior of the head. Since then a large number of diverse technical solutions have been proposed which extend the treatment possibilities or else are intended to hinder or restrict frequently occurring complications.
Until now three different types of valves were able to dominate the market:    1. Valve systems with a simple, rigid differential pressure valve,    2. Valve systems with a post-operative, percutaneously adjustable valve system and    3. Hydrostatic valve systems.
The rigid differential pressure valve of Group 1 is marketed as a sphere-cone construction (U.S. Pat. No. 5,069,663, DE 3020991) as a silicon slot valve or as a diaphragm valve. The valves are distinguished in that their opening behaviour is oriented to the lying position of the patient. In the standing position, such valves lead systematically to unphysiologically low, negative pressure in the head of the patient, which can lead to serious complications.
Representatives of the second group of valves introduce an improvement in that these valves operate like those of Group 1 but allow percutaneous adjustment of the opening characteristics, (U.S. Pat. No. 4,772,257, EP 0 421 557 A2, U.S. Pat. No. 5.928.182, EP 135 991 A1, GB 2143008 A, U.S. Pat. No. 4,551,128, EP 0 060 369). Therefore individual adaptation of the valve function to the individual patients is possible. Nevertheless, these valves do not eliminate the difficulty, either, that the physical conditions in the drainage system of the patient change as a function of posture. If the valves are adjusted to a low opening pressure, this will, on the one hand, favour the clinical outcome, but, on the other hand, simultaneously dramatically increase the danger of over-drainage in the standing position. Conversely, although adjustment to a very high value can reduce the danger of overdrainage, the clinical outcome to be achieved is thus simultaneously lastingly impaired, as the now available opening pressure for the lying position is significantly too high. Valves of Group 3 provide assistance here. Hydrostatic valves are distinguished in that they take into account the changing physical conditions in the drainage system of the patient with the aim of avoiding the problems described above as a result of over-drainage. Three different principles are exploited here.
The oldest construction was produced in the so-called anti-siphon device. According to the same principle, a plurality of different constructions were on the market up to now (EP 0 670 740 B1, U.S. Pat. No. 5,800,376, DE 2752087). Here the effect of the negative pressure at the outlet of the valve is systematically reduced to a minimum. However, opposing this advantage is the serious drawback that the subcutaneous pressure around the valve housing has a considerable influence on the mode of operation of the valve. Owing to tissue growth or an unfavourable position of the patient, this pressure may vary by considerable values and therefore even lead to absolute valve closure. In comparison to conventional valves, these valves have not proved superior, either (Drake, Toronto).
The same is true for the second principle of the third group, the principle of so-called flow control. In flow-regulating valves it is to be ensured that the draining quantity is kept constant independently of the differential pressure at the valve. Whereas in conventional valves the drainage quantity increases proportionally to the differential pressure available, in flow-regulating valves this is impeded (Siphonguard [Codman], Orbis Sigma Valve [Cordis], Diamond Valve [Phoenix]; EP 798 012 A1, U.S. Pat. No. 4,627,832, U.S. Pat. No. 4,776,838). On average the natural liquor production is 23 ml/h. Flow-regulating systems specifically have the following problems.    1. It is technically impossible to ensure the value for the allowed drainage rate. Variances in the course of the production process remain too high (Aschoff, Schoener).    2. The natural variance of the production remains systematically disregarded. If the individual values are too high or too low this can lead both to overdrainage and to under-drainage.    3. The flow regulation is controlled via extremely small cross-sections on the opening mechanism. Particles in the liquor such as, for example cellular constituents have a dramatic influence on function and can easily clog the valve. International comparative studies have shown that this principle was not able to improve the treatment outcomes of hydrocephalus (Drake et al).
In contrast thereto significant improvements were determined after the introduction of gravitation-assisted valves (Meier, Sprung, Kiefer). Two different technical solutions are available on the market. The first approach produces flow control by the gravity-controlled switching over of two valves arranged in parallel (DE 4401422, DE 4307387, EP 94103011). This construction therefore adjusts two different pressure situations in the ventricle system of the patient as a function of his posture. In the second approach, the weight of spheres is exploited to adjust an opening pressure which is changeable as a function of position (EP 0 617 975, EP 0 115 973, DE 19535637). Although many problems could be solved by valve systems of this type the following aspects also remain unsolved here:    1. Adaptation of the valve characteristics to growth or age-related changes or other changes of physiological boundary conditions is not possible.    2. A deliberate, non-invasive adjustment of the valve properties with different adjustments for different body positions of the patient is not possible.    3. Consistent treatment of patients right up to the drainage (which has perhaps become superfluous) being turned off, is not possible.    4. The appropriate adaptation of liquor drainage to individual particularities is not possible.    5. Valves remain a narrow point of discharge. Increase in the drainage reliability by providing wider opening ducts even in the valve seat would be desirable.    6. All previously offered solutions are based exclusively on the differential pressure principle. Other parameters which could also influence sensible control in liquor drainage, are not included. It would be conceivable, for example, to include muscle potentials or other electronic signals. Such signals cannot be taken into consideration in previously offered solutions.    7. Intelligent control, which evaluates as a function of the situation, of valve properties is impossible with previous solutions.    8. Subsequent analysis of incidents is not possible. The explanation for causes for occurrences often stay suppositions.
These problems can partly be overcome by solutions such as are described in DE 19915558 A1. An electronically controlled implant is proposed there which controls the brain pressure of hydrocephalus patients. However, the detection of pressure values in the patient is connected with great uncertainties, and therefore this method is not suitable for satisfactorily controlling the fluid drainage in the long term.
A similar system is described in DE 19654990 A1, in which the drainage quantity through the drainage system is controlled by electromagnetic control elements, for example the characteristics of a spring valve are adjusted, the size of a gap in the discharge, and similar. This necessitates an extraordinarily complicated construction of the valve, and moreover it must be assumed that the controlled variables, i.e. flow and pressure are constant over time and only have to be adjusted if necessary in the course of doctors' visits to then be valid for a longer time period.